In May of 1986, a woman in Orange County, Florida, was surprised by a man who entered her apartment and raped her at knifepoint. Despite the fact that she got a glimpse of his face, the chances of identifying and convicting her rapist were slim. Although law enforcement officers did their best to identify the perpetrator, their investigative techniques in the case were limited compared to our current set of forensic tools. That changed when Jeffrey Ashton, an assistant attorney for the state of Florida, saw an advertisement for DNA-based paternity testing in a magazine and began to wonder if DNA testing could also be used to identify the man responsible for the attack.
Throughout the remainder of 1986, 22 other women were sexually assaulted in a similar manner. Each time, the attacker gained entry through an unlocked window or door. He concealed his face during the attack and was careful not to leave fingerprints to avoid identification. At the time, forensic investigators’ only statistical method of identification was serology, which is the analysis of proteins in blood and other body fluids such as semen. The power of discrimination obtained through serological analysis is very low compared to that of modern DNA typing, so it was difficult to definitively identify the assailant based on serology alone. Investigators needed more evidence. The discovery of two fingerprints on a window screen at one of the crime scenes raised hopes of a positive identification, but unfortunately, the fingerprint analysis yielded no match in the database. Law enforcement officers were back to square one.
The big break in the case came in March of 1987 when a woman called police to report a prowler. When police apprehended the man and analyzed his fingerprints, they discovered a match with those from the window screen. That man was Tommie Lee Andrews.
The legal case against Andrews was strong. In addition to the fingerprint match, the first victim identified him as her attacker, and the serological analysis of semen left at the crime scenes matched that of Andrews. However, prosecutors wanted to do everything possible to maximize their chances of convicting the man who had assaulted so many women in their community.
That’s when then-state prosecutor Jeff Ashton approached Assistant State Attorney Tim Berry with an idea. Ashton had seen a magazine advertisement for DNA testing to resolve paternity disputes. Why couldn’t that same technology be used to identify the assailant?
It was a question worth pursuing, so prosecutors contacted Lifecodes Corp., a New York research lab that was conducting DNA-based paternity tests. One of the senior scientists at LifeCodes, Michael Baird, saw no reason that DNA couldn’t be used in a criminal investigation, saying that the test ”is applicable to anything that would have DNA in it—bloodstains, semen, dead tissue, dental pulp, bone marrow”. LifeCodes agreed to perform the DNA testing.
At the time, DNA testing was in its infancy but was quickly proving its worth in resolving an immigration case in England (1) and paternity disputes. In addition, DNA evidence had entered the realm of criminal investigation in a parallel case in England, where Colin Pitchfork was accused of the rape and murder of two young girls. However, DNA evidence had never been presented in a U.S. court, and Andrews’ defense team fought to exclude it on the basis that DNA testing was unproven and that Lifecodes, the only company that performed DNA typing, was trying to profit by increasing the market for such tests. However, after an independent DNA expert testified as to the accuracy and scientific validity of this new technology, the judge in the case allowed the DNA evidence to be admitted. Even though the technology used back in 1986—restriction fragment length polymorphism—was not as sensitive or discriminative as today’s methods, DNA testing revealed that there was only a 1 in 10 billion chance that the match between Andrew’s DNA and DNA found at the crime scenes was a random match.
Based on both fingerprint analysis and DNA typing, Tommie Lee Andrews was convicted of rape in November of 1987 and sentenced to prison for 22 years, making him the first person in the U.S. to be convicted as a result of DNA evidence. In subsequent trials, he was convicted of additional assaults and was sentenced to a total of 100 years behind bars.
To reflect on this important advance in forensic science, Michael Baird and Jeff Ashton will be presenting The Birth of DNA Testing: A 25-Year Prospective at the 25th International Symposium on Human Identification. For more information, visit ishinews.
- Jeffreys, A.J., Brookfield, J.F. and Semeonoff, R. (1985) Positive identification of an immigration test-case using human DNA fingerprints. Nature 317, 818–9.
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